The object of this paper is to investigate Richardson
extrapolation of two different schemes for finite element
approximations of a linear parabolic partial differential equation
with a homogeneous Dirichlet boundary conditions, which can lead
significantly to the improvement in the accuracy of approximations
with the help of an interpolation postprocessing technique. As a
by-product, we illustrate that all the approximations of high
accuracy can be used to generate a posteriori error estimators.